Spark plug



Patented Sept. 15, 1936 UNITED STATES ,SPARK PLUG j VEdward w. Mitchel, Detroit, Mich. VAmilication December 19,1935, Serial No. .55,169

6 Claims.

My invention relates to a, new and useful improvement in .a spark plug and has for its object the Vprovision of'a sparkY plug which will be simple in structure, economical vof manufacture,

durable, easily and quickly assembled, compact and `highly eicient in use.

Another object of the invention `is the provision of a spark plug having an electrode provided with a. circular opening, the edge of which 10 serves as a sparking point, thus providing an infinite number of `points which may serve as sparking points.Y

Another object of the invention is the provision of a'spark plug so constructed and arranged so as to provide with the cylinder chamber a pair of vexplosion chambers, one of the chambers being in the cylinder and the other in the pocket formed in the plug so that the sparking takes place directly across a column of .compressed gases, thus adding to the eiliciency of the spark plugy in itself and to the eilieiency of the engines.

Another object of Ythe invention is the provi- ASion'of a spark plug so constructed and arranged that Vit will maintain itself in a clean condition and free from carbon. Y.

Other objects will appear hereinafter.

The invention consists in .the combination and arrangement of parts hereinafter described and claimed. Y

The invention will 'be best understoodV by a reference to the accompanying drawing which forms a part of this specification, :and in which, Fig, 1 is a longitudinal, sectional, central view of the invention. Y

Fig. 2 is a top plan view of the invention.

Fig, 3 is a fragmentary, longitudinal, central, sectional view of arslightly modified form of the invention.

As shown in the drawing, the invention comprises a metallic shell 1 having the threaded p0rtionY 8 Vwhich threads into an opening formed in the engine head. This shelly 1 is tubular and is enlarged as at `El to provide clearance for the peripheral rib I0 formed on the insulating shell n. :siam nui-.lz threads into the upper end of the shell 1 and engages against the rib- I0 to force the insulating shell I I inwardly of the shell 1 and prevent its removal therefrom so as to lock the parts in assembled relation. A metallic electrode I3 projects through the insulating core or shell II and is provided on its upper end with the threaded stem I4 for the reception of the binding nut I5 whereby electrical contact may be made with a wire. The

lower end of the electrode is provided with a Centrally arrangedY inwardlyV projecting pocket I5 which opens through the constricted neck or passageway 2l.. It will be noted .that the .electrode at the pocket bearing end terminates flush with the corresponding end of the insulating 5 shell or core H. Insulating Washers I1, formed from.V mica or the like, serve to separate the end of the electrode I3 and the end of the insulat-I ing shell II from the inwardly turned endY I8 of the shell 1. This shell 1 is formedcup-shaped 19 and the inwardly turned end I8, referred to, is the lbottom of the cup-shaped structure and through this bottom is formed the opening i9 which is of the same diameter as the constricted portionv 2li-and which registers therewith. YA 15' corresponding `opening is 'formed through theA washers I1, which,` as stated, are preferably formed from mica, although any other suitable insulating material may be used. The outer end of the opening i9 is flared as at 22 to pro-Y 2c ation of the spark gap is made. this manner 30k the plug may be adjusted for use in engines of variablefpressures. Experience has shown that the higher the compression attained in the engine, tllesrnaller should be the spark gap.'V In use the sparkingwill take place between Vthe surface of the opening I9 and the end, at the inner f'surface, of the constricted portion 2l and since this constricted portion or passage'l is formed parallel in cross section, a multiplicity of sparking points is thus provided. Once the plug 40' is assembled with the proper number of washers so that Lthe proper adjustment of the spark gap has been made, the plug will have a constant sparking gap as there'will be no relative' movement-of the separated lsparking points due to 45 expansion or contraction as is the case where a wire prong is projected outwardly from the metallic shell or where a central wire electrode is used. Furthermore, because of the multiplicity of sparking points, wear and pitting is prac- 50 tically obviated.

It will also be obvious that as the engine moves on to the compression stroke, the' compressed gas will be forced through the constricted passage 2l into the pocket. I6 and when the 55 `sparking takes effect, the gas in this pocket will be exploded and likewise the gas in the opening I9 and the Vpassage 2| will be exploded, thus communicating with thegas in the cylinder. k In thismanner I have provided a spark plug which produces, in conjunction with the cylinder, a

. pair of exploding chambers, the cylindei` serving as one exploding chamber and the pocket I6 as theother exploding chamber. As the exploding takes place, thegas in the pocketvl will be violentlyrexpelled through the constricted pas- Y sage 2I and because of the ared outer side of Yao the opening I9 a Venturi effect in the movement of the gas is present. As this exploded gas is forced outwardly through the passage 2l, it -wlll serve to effect a cleaning of the sparking points,

'thus maintainingl the Y plug free from carbon.

It is also believedr obvious that the diameter of the constricted portion 2l VmayV bevaried with spark plugs operating Runder different conditions and the depth of the pocket I6 may also be varied, a

larger pocketv I6 being desirable on lowercom'- pressions.

In Fig. 3, I haveillustrated the invention used in a mannerrin which Vthe shell-If` is turned Yinwardly as at 23 atits upper end to provide the Y channel 24. The insulating shell or core Il isV molded in the shell 'I' so that there is thus provided a molded shoulder 25 which engages in the Vchannel 24. This construction renders it possible to form the shell .'I' in a very economical manner land preferably by a stamping process.

It is also apparent thatV the machine Work on the shell 'I' isv considerablyfreduced over vthat required for the shell "I, illustrated in Fig. k1.A The spark plug in all other respects is possessed of the same ,structural detailand of the same advantages as enumerated for Vthe form shown inrFig. 1.

YWhile I have illustrated Aand rdescribed the preferred formV of construction, I do not Vwish to limitY myself to theAprecise details of structure shown, but desire to'avail myself of such modifications and variations Vas may come `within the scope of the appended claims.

Having thus described my invention, what I claimas new and desire to secure by Letters Pat- Ventisz Yl. YA spark `plug ofthe Yclass described, com-Y prising: a shell; an insulatingmember'mounted in said shell; an electrode Yprojecting through Ysaid insulating member and. terminating flush with one end thereof; an inwardly turnedrportion on the inner end of said shell; and insulating means Apositioned Yon said inwardly turned portion land spacing the same from'the Vencl of saidelectrode.

electrodev from said bottom.

2. A spark plug of the class described, comprising: a shell; Van insulating member mounted in said shell; an electrode projecting through said insulating member and terminating flush with one end thereof; an inwardly turned portion Von the inner end of said shell; and insulating means positioned on said inwardly turned portion and spacing the same from the end of saidelectrode,

said electrode having an axially directed pocket formed in said end. Y 1

3. A spark plug `of the class described, comprising: a cup-shaped shell having an opening formed centrally in its bottom; an insulating core projected into said shell; `an electrode extending through said core `and terminating at its inner end iiush with the end of said insulating member; layers of insulation on said bottom having openings formed therethrough registering with the yopening in said bottom and spacing said 4. A'spark plug of theclass described,.co`m prising: a cup-shaped shell havingan'opening formed centrally in its bottom; an insulating core projected into said shell; electrode ex tending through' said vcore andrterminating at its inner end flush with the end of fsaid insulating member; layers of insulation on said bottom having openings formed therethrough'. registering with the Yopening in said Vbottom: and spacing said electrode from said bottom,. said'electrode having an axially extending pocket formed therein registering with the openingsin said insulating members and said bottom.;

5. A spark. plug of the class described, com` prising: acup-shaped shell having an opening formed centrally in its bottom; an insulating core projected into said shell; ian electrode ex- Y tending through said core and terminating at its inner'end flush with the end of said insulating Y member; insulation positioned between saidbottom'and the end of said `electrode for spacing the same` from said bottom, vsaid insulation having` an opening formed therethrough'registering with the opening in said bottom, said electrode having an axially extending pocket formed therein andV terminatingwith a constricted outlet passage registering with the openings insaid'bottom.;

6. A spark plug 'of the class described, comprising: a cup-shaped shell having an opening formed'centrally in its bottom an insulating core projected.A into vsaid shell; an electrode extendingVV through said core and terminating at its innerV endflush with `the end of Vsaid insulating menrber; insulation positioned between said bottom and the Vend 'of said electrode for spacing the same from said bottom, said insulation having Van opening formed therethrough Vregistering with the opening in said bottom, said electrode hav# lng an axially extending pocket formed therein sage registering with the openings in said bot' tom, the .outerfend of the opening in said}bot tom being flared outwardly toprovide aventurl eiect.

EDWARD "W.

and terminating with a. constricted outlet lpas,- 

